Founder of Pershing Square — one of America's best-known and most polarizing activist investors.
Life story
Bill Ackman was born in 1966 in Chappaqua, New York. His father, Lawrence David Ackman, was chairman of the real estate finance firm Ackman-Ziff Real Estate Group; his mother is Ronnie Ackman. The family is of Ashkenazi Jewish descent.
He graduated from Horace Greeley High School in 1985, then earned a bachelor's degree in social studies from Harvard College magna cum laude in 1988. In 1992 he completed an MBA at Harvard Business School.
How they got started
In 1992, the year he finished his MBA, Ackman co-founded the investment firm Gotham Partners with Harvard classmate David Berkowitz. By 1998 it managed about $500 million. Later, Ackman's bet against MBIA's bonds paid off during the 2008 financial crisis.
In 2004 he launched Pershing Square Capital Management with $54 million of his own money and capital from Leucadia National. From the start, the fund relied on activism: buying a large stake and pushing management on strategy, governance and costs.
In October 2014 the fund's closed-end vehicle, Pershing Square Holdings, listed in Amsterdam, raising $2.73 billion. That permanent capital let the fund take long-term positions without fear of sudden investor redemptions.
Investment style
Ackman runs a highly concentrated portfolio — typically just 8–12 companies. He favors simple, predictable, cash-generative businesses with durable competitive positions (restaurant chains, railroads, hotels, real estate). He often takes a large stake and pushes management for change, launching proxy fights when needed.
Another hallmark is openness: Ackman defends his ideas publicly through presentations and social media. Sometimes that has produced big wins, sometimes big and very public mistakes.
Best decisions
Canadian Pacific Railway (2011–2012)
Ackman built a large stake in the railroad and launched a proxy fight to replace management. Close to 90% of shareholder votes backed his slate, and the company sharply improved efficiency under new leadership. The Globe and Mail named him "CEO of the Year" for the campaign.
COVID-19 hedge (2020)
Anticipating the pandemic's market shock in early 2020, Ackman spent about $27 million on credit hedges. In less than a month they produced $2.6 billion in gains — one of the most famous hedges on record.
Chipotle Mexican Grill (from 2016)
He bought a large stake after food-safety scandals had crushed the stock. The company recovered in the following years and remained among the fund's top holdings from 2017 to 2024.
Universal Music Group (2021)
Pershing took roughly a 10% stake in the world's leading music-rights company, and Ackman sat on its board from 2022 to 2025. UMG became one of the fund's largest positions.
Biggest mistakes
Valeant Pharmaceuticals (2015–2017)
The big bet on the drugmaker cost the fund roughly $4 billion. Ackman sold the remaining shares in March 2017 for about $300 million. It was the main driver of the fund's difficult 2015–2018 stretch.
Herbalife short (2012–2018)
Ackman called Herbalife a pyramid scheme, bet $1 billion against it and turned it into a public campaign, with Carl Icahn on the other side. The stock never collapsed, and Ackman exited at a loss in February 2018.
J.C. Penney (2010–2013)
The turnaround plan for the department-store chain failed; after disagreements with fellow directors, Ackman left the board.
Netflix (2022)
A short-lived Netflix position was closed within months at a loss of more than $430 million — Ackman openly admitted his thesis had been wrong.
Today
In 2026 Ackman is 60 and still runs Pershing Square (assets under management were reported at about $19.7 billion in May 2025). In August 2024 he planned an IPO of a new U.S. closed-end fund, Pershing Square USA, but withdrew it after attracting only about $2 billion of demand.
In May 2025 Pershing raised its stake in Howard Hughes Holdings to about 47%, and Ackman returned as executive chairman. He has said he wants to turn Howard Hughes into a diversified holding company along Berkshire Hathaway lines.
What to learn from following the portfolio
- Ackman holds few, large positions — when the fund adds a new company, it usually reflects deep work and a multi-year intent. New positions are the most interesting signal to watch.
- He often enters as an activist, so the stock's fate depends on the campaign's outcome. "Ackman bought it" is not an automatic win — Valeant and Herbalife prove that.
- 13F filings lag by up to 45 days and show only long U.S.-listed positions: Ackman's hedges, shorts and European holdings (such as UMG) may not be fully visible.
- Halal lens: his favorite sectors — restaurants, consumer, railroads, real estate — include companies that may pass halal screens, but debt levels and revenue sources vary widely. Financials like Fannie Mae/Freddie Mac are typically not halal. Check each position's halal status on the Portfolio tab.
An introduction based on public sources — not investment advice. Spotted an error? Let us know.